Up to now, various methods have been proposed for improving the absorption speed of water-absorbable resins which are used as absorbents for a paper diaper and the like, some of them as described below are based on a concept of increasing the area contacting with a liquid to be absorbed by broadening the surface area of the water-absorbable resins.    a. A method of rendering a water-absorbable resin porous by adding a low-boiling point volatile solvent to a polymerization solution to be used in the manufacturing process of the water-absorbable resin, and vaporizing the volatile solvent with polymerization heat (Japanese Patent Application Laid-Open No.S59-18712 (1984));    b. A method of forming a foam type resin by blending a carboxyl group-containing water-absorbable resin and glycidyl group-containing polyolefin resin with a crosslinking agent and pyrolytic foaming agent, and then foaming the mixture with heat (Japanese Patent Application Laid-Open No.S63-251437 (1988));    c. A method for obtaining a porous water-absorbable resin by dispersing a foaming agent consisting of an azo compound containing an amino group into an aqueous solution containing an unsaturated monomer and crosslinking agent, and by conducting polymerization (Domestic Re-publication of PCT Publication No. WO96/17884);    d. A method of granulating fine particles using water, a hot-melt resin binder and the like;    e. A method of coating the surface of a water-absorbable resin in a composition with porous inorganic particles so that the weight ratio of the resin to the inorganic particles falls within a range of 10/90 to 90/10, wherein the composition consists of a mixture of particles of the water-absorbable resin and the inorganic particles (Japanese Patent Application Laid-Open No.H8-10616 (1996)).
However, these methods were not sufficient in terms of performance and a production process.
Further, it has recently been suggested to improve the absorption speed by a method in which the surface area of a water-absorbable resin is increased by least 10% by building a micro-filler into the water-absorbable resin (International Publication No. WO99/03577).
In said method, the improvement of the absorption speed is recognized for a liquid to be absorbed containing water-insoluble or hardly water-soluble matters such as menstrual blood or feces, however, the further improvement of the absorption speed and absorption amount of the liquid is desired because of the increased demand from the market.
The inventors have intensively studied considering the above-mentioned problems, and as a result, have reached to the present invention with a finding that the diffusion/absorption speed and absorption amount of a liquid to be absorbed are improved by using a water-absorbable resin obtained by polymerization in the presence of a complex compound (d) of a metal element (d1) and a ligand (d2) in which the ligand is an anion or a neutral molecule, in combination with a water-insoluble nonporous spherical monoparticle having a specific average particle diameter.
The present invention is directed to provide absorbents having an excellent diffusion/absorption speed and absorption amount of a liquid to be absorbed inside the absorbable resin, and to provide a process for producing the same, wherein the liquid to be absorbed contains water-insoluble or hardly water-soluble matters such as menstrual blood or feces. Further, the another purpose of the present invention is to provide absorbable constructs and absorbable articles showing an excellent absorption performance when the absorbents of the present invention are applied to sanitary goods such as a sanitary napkin.